She was in possessions of a Vietnamese travel document when she was busted.
He died en route to the hospital Monday after some sort of encounter at the Kuala Lumpur International Airport.
Malaysian police investigating the attack said the cause of Kim's death was not yet known and a post-mortem would soon be carried out.
Sky's Asia Correspondent Katie Stallard said: "In terms of motive, perhaps he (Kim Jong-Nam) could have been seen as a threat to Kim Jong-Un's leadership - certainly that is being suggested as one theory behind his killing".
Kim Jong Nam and Kim Jong Un have the same father, late dictator Kim Jong Il, but different mothers. Nam Sung-wook at Korea University said, "Kim Jong-un now marks his fifth year in power and seems to have done some pruning to streamline his leadership structure". He told medical workers before he died that he had been attacked at the airport with a chemical spray, the Malaysian officials told the AP.
According to The Sun daily, she had stayed at a hotel 20 minutes away from the KL International Airport 2 (KLIA2) since Monday.
In the nation's patriarchal dynasty, Kim Jong Nam, 45, represented a possible alternative if elites ever moved to oust Kim Jong Un, 33.
Even Kellyanne Conway Can't Spin Michael Flynn's Sudden Resignation
After some time , White House press secretary Sean Spicer issued a statement saying: "The President is evaluating the situation". Flynn's resignation comes as Trump and his top advisers seek to steady the White House after a rocky start.
Still photos of the video, confirmed as authentic by police, showed a woman in a skirt and long-sleeved white T-shirt with "LOL" across the front.
NIS officials believe two women approached Kim and poisoned him as he was waiting in line for a flight to Macau, according to the lawmaker, although he added they were waiting for the autopsy report.
News of the murder came two days after Kim Jong Un test-fired a ballistic missile as part of efforts to develop North Korea's nuclear-weapons capability. While details remain sketchy, it is widely believed that the killers were sent by the North Korean regime.
The South Korean government on Wednesday also urged all North Korean defectors to take extra precautions for their own safety and security. Initial reports on Tuesday said he was killed by poisoned needles, but Mr Kim apparently told airport staff that some liquid was splashed on him. The South Korean embassy in Washington, D.C., said it did not have independent confirmation of the reports but was monitoring media coverage.
North Korea has demanded Malaysia immediately return the body of Kim Yong-nam - its leader Kim Jong-un's half-brother - following his apparent assassination.
Kim Jong-un had issued a "standing order" for his half-brother's assassination.
His downfall started when he was caught in 2001, along with his wife and son, trying to enter Tokyo on false passports.